Time and Temperature Dependent Tetraparametric Bolt Assembly Model

Abstract

Various factors contribute to leakages in bolted pipe flange connections, with external loads, especially those caused by misalignment, being significant. Misalignment creates an external axial load and bending moment, potentially causing flange separation, leading to leaks. Although numerous studies have investigated these effects, practical solutions are lacking. This study explores the tetra-parametric assembly method, a numerical approach that iteratively calculates non-uniform bolt tightening load distribution, and the impact of operating temperature on the leakage of an HDPE stub-end connection. This study integrates the temperature and stress relaxation effects on HDPE and evaluates the deterioration in connection efficacy over time employing finite element methods, FEA. A calibrated non-linear three-network model (TNM)that accurately forecasts the material mechanical response and the general constitutive viscoelastic-plastic behavior of HDPE is utilized in the computational simulations to evaluate the annual HDPE connection’s leakage characteristics across several isothermal conditions; 23, 40, 60, and 80 ◦C. FEA findings demonstrate that the connection is prone to leakage at isothermal conditions, i.e. temperatures, due to inadequate bolt preload, with leakage occurring sooner at higher temperatures. To simulate real-world operation conditions akin to an above-ground piping system for a specific geographical location, an annual temperature prof ile was applied to the FEA model, simulating leakage occurrence across one service year. The obtained results informed various plans for bolt re-torquing that were evaluated to provide recommendations for optimal bolt re-torquing practices to prevent leakage throughout the expected operation lifetime of the connection incorporating HDPE components.

Date of Award	26 Aug 2024
Original language	American English
Supervisor	Imad Barsoum (Supervisor)